266 Dr. Prout on the Phenomena of Sangwification, [Avrin, 
that the air-bladders of fishes contain oxygen gas, whichis usually 
greater in proportion as the animal imhabits deeper waters,* 
@ circumstance which appears to indicate their use to be some- 
what analogous to that of the organs of respiration.+ In animale 
inferior to fishes, the same phenomena oecur, Thus it was early 
observed by Ray, that msects died very soon if the holes or stig- 
mata through which the air enters into their bodies were stopped 
with oil or honey. Derham found also that wasps, bees, hornets, 
also snails, leeches, &c. soon died under the exhausted receiver 
ofan air-pump ; and Scheele and Bergman found that like other 
animals, they converted the air of the atmosphere into carbonic 
acid. Vauquelin, however, was tne first that made accurate and 
satisfactory experiments with insects, in which he proved beyond 
a doubt the accuracy of the above conclusions. This chemist 
also extended his experiments to the molusca, and obtained 
precisely the same results; as did Spallanzani, and more 
recently Haussman.{ Lastly, Sir Humphry Dayy found that 
even the zoophytes produced similar phenomena.§ Thus then it 
appears, that all animals convert the oxygen of the atmosphere 
mto carbonic acid gas; and as the blood is the fluid which 
appears to be operated upon, and to produce this remarkable 
change in the more perfect animals, we may doubtless conclude 
that a similar fluid, or one that performs a similar office, is the 
cause of this change in the inferior animals, although we cannot 
discover its existence. 
Secondly, We come to consider whether any other gas can 
be substituted for oxygen in respiration. This question was very 
early decided in the negative. It was also found that animals 
could not respire even oxygen for any length of time without 
dilution, and in short that no other compound, except atmospheric 
air, im which the proportion of oxygen is only one-fifth of the 
whole bulk, is capable of supporting life. Pure oxygen and 
gaseous mixtures containing a larger proportion of this gas than 
atmospheric air, appear to destroy life in a short time by over 
excitation. On the contrary, some gases of a mild and inactive 
character, as hydrogen and nitrogen, when pure, or in too large 
proportion, destroy life by the opposite means, or suffocation ; 
while others, as carburetted hydrogen, carbonic acid, &c. seem 
to prove fatal simply in virtue of their deleterious properties. 
Agreeably to what might be expected are the effects which these 
different non-respirable airs produce upon the blood out of the 
* See Berzelius’s View of the Progressand Present State.of Animal Chemistry, 
p. 44. Also Annals of Philosophy, vol. v. p. 40. 
+ See an excellent paper on the respiration of fishes, recently published by 
“MM. Provencal and Humboldt, in Mem, d’Arcueil, ii, 259. Those gentlemen 
fowid that fishes not only convert oxygen gas intu carbonic acid gas, but that a 
considerable proportion botir.of oxygen and azote is absorbed during the respira 
tory process, 
+ See Johnson's History of Animal Chemistry, vol. iii. 
4 See Davy on Respiration, in Deddoe’s Medical Coatributions, 
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